\begin{table}[tbp] \centering
\newcolumntype{R}{>{\raggedleft\arraybackslash}X}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcolumntype{C}{>{\centering\arraybackslash}X}

\begin{tabularx}{\linewidth}{lcc}

\toprule
{tdef}&{treated}&{untreated} \tabularnewline
\midrule \addlinespace[\belowrulesep]
binary treatment, 100\% reassigned&280&338 \tabularnewline
\midrule binary treatment, 50\%+ reassigned&372&246 \tabularnewline
\midrule continuous treatment, (\% addresses reassigned or Δdistance)&513&105 \tabularnewline
\bottomrule 

\end{tabularx}
\end{table}
